[PATCH u-boot-marvell RFC] PLEASE TEST: ddr: marvell: a38x: fix BYTE_HOMOGENEOUS_SPLIT_OUT decision

[Stefan Roese]

On 2/16/22 14:26, Marek Behún wrote:
> On Wed, 16 Feb 2022 09:41:44 +0100
> Stefan Roese <sr at denx.de> wrote:
> 
>> On 2/15/22 23:21, Chris Packham wrote:
>>> On Fri, Feb 11, 2022 at 5:25 AM Marek Behún <kabel at kernel.org> wrote:
>>>>
>>>> From: Marek Behún <marek.behun at nic.cz>
>>>>
>>>> In commit 3fc92a215b69 ("ddr: marvell: a38x: fix SPLIT_OUT_MIX state
>>>> decision") I ported a cleaned up and changed version of patch
>>>>     mv_ddr: a380: fix SPLIT_OUT_MIX state decision
>>>>
>>>> In the port we removed checking for BYTE_HOMOGENEOUS_SPLIT_OUT bit,
>>>> because:
>>>> - the fix seemed to work without it
>>>> - the bit was checked for only at one place out of two, while the second
>>>>     bit, BYTE_SPLIT_OUT_MIX, was checked for in both cases
>>>> - without the removal it didn't work on Allied Telesis' x530 board
>>>>
>>>> We recently had a chance to test on more boards, and it seems that the
>>>> change needs to be opposite: instead of removing the check for
>>>> BYTE_HOMOGENEOUS_SPLIT_OUT from the first if() statement, the check
>>>> needs to be added also to the second one - it needs to be at both
>>>> places.
>>>>
>>>> With this change all the Turris Omnia boards I have had available to
>>>> test seem to work, I didn't encounter not even one failed DDR training.
>>>>
>>>> As last time, I am noting that I do not understand what this code is
>>>> actually doing, I haven't studied the DDR training algorithm and
>>>> I suspect that no one will be able to explain it to U-Boot contributors,
>>>> so we are left with this blind poking in the code with testing whether
>>>> it works on several boards and hoping it doesn't break anything for
>>>> anyone :-(.
>>>>
>>>> Signed-off-by: Marek Behún <marek.behun at nic.cz>
>>>
>>> Tested-by: Chris Packham <judge.packham at gmail.com>
>>
>> Reviewed-by: Stefan Roese <sr at denx.de>
> 
> Dear Stefan,
> 
> will you apply this (removing the PLEASE TEST: prefix) or should I send
> it again without it?
> 
> I am going to send another patch which will reset the board immediately
> if DDR training fails, so I can send with that one.

Whatever you prefer. Plan is to apply/push some of the pending patches
in the next few days.

Thanks,
Stefan